where <math> R=|r-r'| \text{, } k_0 = \tfracfrac{2\pi}{\lambda_0} \text{ and } Z_0 = 1/Y_0 = \eta_0 </math>.
When k<sub>0</sub>r >> 1, i.e. in the far-zone field of the scatterer, one can use the asymptotic form of the Green's functions and evaluate the radiation integrals using the stationary phase method to obtain far-field expressions for the electric and magnetic fields as follows: